The present invention relates to a device for fixing a steering wheel to a steering shaft.
Conventionally, assembling of a steering wheel of motor vehicles is carried out as follows. With an air-bag device mounted in advance, a steering wheel is provided to an assembling process where the steering wheel is fixed to a steering shaft, then a connector on the vehicle-body side is connected to an outside terminal of a rotary cable connector on the steering-wheel side. According to this assembling method, examination and quality control of the air-bag device, horn switch, etc. can be carried out in advance in another process, resulting in excellent assembling efficiency and improved yield of steering wheels. A steering wheel suitable for this assembling method is known, for example, in DE 44 15 765 A1 and JP-A 9-226600.
With a fixing device for a steering wheel as disclosed in DE 44 15 765 A1, a serration formed at a boss of the steering wheel is engaged with a serration formed at an end of the steering shaft, then a fixing screw of the boss is tightened to have an end fit in an annular groove of the steering shaft, obtaining the steering wheel fixed to the steering shaft.
With a fixing device for a steering wheel as disclosed in JP-A 9-226600, both ends of a yoke engaged with a serration of the steering shaft are tightened by a bolt to reduce, the diameter of the yoke, obtaining the steering wheel fixed to the steering shaft.
The apparatus of each reference includes an air-bag device mounted in a pad integrated with the steering wheel.
With the known fixing device for a steering wheel wherein the serration of the steering wheel is engaged with that of the steering shaft to mount the steering wheel to the steering shaft, when detaching the steering wheel from the steering shaft, the serration of the steering wheel should be separated from that of the steering shaft by using a screw tool such as a puller.
With the known apparatus including the air-bag device mounted in the pad integrated with the steering wheel, however, since the boss for connecting the steering shaft and the steering wheel is concealed by the pad, which forms an obstacle for applying the screw tool, causing an inconvenience of difficult removal of the steering wheel, etc.
When using taper serrations to mount the steering wheel to the steering shaft, the taper serrations are firmly engaged with each other through tightening upon mounting of the steering wheel, causing another inconvenience of time-consuming removal of the steering wheel, etc.
If the angles of the taper serrations are reduced to prevent such inconvenience, a backlash is apt to occur between the steering wheel and the steering shaft after mounting, requiring increased machining accuracy of the taper serrations.
However, increasing of the machining accuracy of the taper serrations requires the use of an accurate machine and a lowering of a machining speed, reducing the productivity, resulting in increased manufacturing cost. Simple adoption of severe dimension control increases a proportion defective to deteriorate a yield of steering wheels and cause difficult assembling due to reduced clearance between two engaged parts. Therefore, even if, as shown in the above reference, the steering wheel and the air-bag device are modularized to rationalize a vehicle-body assembling process, inconveniences arise such as increased manufacturing cost and assembling time.
It is, therefore, an object of the present invention to provide a fixing device for a steering wheel that enables easy mounting and detachment of the steering wheel with a steering-wheel main body and an air-bag device modularized.
One aspect of the present invention lies in providing an arrangement, comprising:
a steering shaft having an axis and an end formed with a groove in a direction of intersecting said axis, said end including a first rotation stopper and a first fit-amount restrainer;
a steering wheel;
a boss fixed to said steering wheel, said boss including a second rotation stopper engaged with said first rotation stopper of said steering shaft and a second fit-amount restrainer abutting on said first fit-amount restrainer of said steering shaft, said boss detachably mounting said steering wheel to said steering shaft;
a fixing device mounted to said boss, said fixing device pressing said boss in a first direction of engaging said steering wheel with said steering shaft, said fixing device being engaged with said groove of said steering shaft; and
a pressing device mounted to said boss, said pressing device pressing said steering shaft in a second direction opposite to said first direction so as to release said steering wheel from said steering shaft.
Another aspect of the present invention lies in providing an arrangement, comprising:
a steering shaft having an axis and an end formed with a groove in a direction of intersecting said axis, said end including a first rotation stopper and a first fit-amount restrainer;
a steering wheel;
a boss fixed to said steering wheel, said boss including a second rotation stopper engaged with said first rotation stopper of said steering shaft and a second fit-amount restrainer abutting on said first fit-amount restrainer of said steering shaft, said boss detachably mounting said steering wheel to said steering shaft;
means mounted to said boss for pressing said boss in a first direction of engaging said steering wheel with said steering shaft, said boss pressing means being engaged with said groove of said steering shaft; and
means mounted to said boss for pressing said steering shaft in a second direction opposite to said first direction so as to release said steering wheel from said steering shaft.